A. Field of the Invention
This invention relates to a foldable bicycle that folds on or near the seat tube having non-overlapping front and rear frames and using quick release clamps or other means to lock a front and a rear frame together in the open riding position. In this application, the term "quick release" or other locking devices are referred to as restraining devices.
B. Prior Art
Many folding bicycles such as the Dahon, U.S. Pat. No. 4,067,589, require many folding steps while setting the folding axis in the middle of the structural members making a bicycle that is too complicated to fold and structurally weak. To date the strongest folding bicycles have been those that fold about the seat tube using a minimum number of quick release levers. U.S. Pat. No. 4,448,437 and U.S. Pat. No. 4,900,047 define a fold about the seat tube construction, with the rear member collared about the front member and the seat post attached to the front member.
Other bicycles, such as the Bridgestone "Grandtech", U.S. Pat. No. 4,579,360, employ the fold about the seat tube concept and involved only a few steps to fold the bicycle but had to sacrifice the strength of the open bicycle by distorting the seat post to achieve the limited number of folding steps. Likewise, U.S. Pat. No. 5,222,751 uses the concept defined in U.S. Pat No. 4,448,437 by having the same bottom bracket area collar as shown in FIG. 2B of U.S. Pat. No. 4,448,437. The design has a collared bent seat tube attaching a front and a rear frame, at the bottom near the crank and at the top near the seat tube.
All of these bicycles and tandems, including the prior configurations of the present inventor, had front and rear frames that partially or completely overlapped each other. U.S. Pat. No. 4,448,437 shows both the condition where the front frame surrounds the rear frame and where the rear frame surrounds the front frame. The current application has the front and rear frames partially overlapping. U.S. Pat. No. 4,579,360, Bridgestone's "Grandtech" has the back frame surrounding the front frame and U.S. Pat. No. 5,222,751 has the two frames overlapping.
There are however still areas for design improvement, to reduce the number of components, to increase strength of the frame and to enhance and simplify the folding operation. In this application a novel non-overlapping frame design of this invention has neither the front nor the back frame overlapping the other. The hinge points or restraining points may project into the opposite frame area but they are not the basic mass of the distinct frames. There are no other folding bicycles or tandems with non-overlapping back and front frames. There have been many recumbants and bicycles designed with a continuous single bar running from the head set to the back wheel axle, those that folded had a door type hinge in the middle, creating overlapping frames when folded. None of these had non-overlapping front and rear frames.